Hydrogen biofuel has the potential to solve a variety of challenges related to the global need for a clean and sustainable form of energy. Hydrogen can be produced from a variety of domestic resources including: fossil fuels such as natural gas and coal; renewable resources such as solar, wind, and biomass; or nuclear energy. The current challenge, however, is to develop technologies for hydrogen production from these resources that are clean, efficient, and cost effective.
Photobiological processes, specifically those which involve the production of hydrogen from specialized microorganisms, offer an attractive long term renewable mechanism of hydrogen production that will minimally impact the environment (Gest, et al. “Studies on the Metabolism of Photosynthetic Bacteria. V. Photoproduction of Hydrogen and Nitrogen Fixation by Rhodospirilum rubrum,” J. Biol, Chem. 182:153-170 (1950); Das, et al. “Hydrogen Production by Biological Processes: A Survey of Literature,” Int. J. Hydrogen Energy 26:13-28 (2001); Prince & Kheshgi, “The Photobiological Production of Hydrogen: Potential Efficiency and Effectiveness as a Renewable Fuel,” Crit. Rev. Microbial. 31:19-31 (2005)). For this technology to be commercially efficient, however, these hydrogen producers must be identified and potentially modified for optimized production.
Microbes possess two enzymes, hydrogenase and nitrogenase, which produce hydrogen either directly through fermentation, or indirectly as a by-product of other metabolic processes. Nitrogenases are chiefly involved in the conversion of nitrogen gas to ammonia with the concomitant obligate production of hydrogen during the process of nitrogen fixation. This difficult reaction requires large amounts of ATP and reductant and, therefore, does not represent an efficient method of hydrogen production in terms of commercial utility (Simpson & Burris, “A Nitrogen Pressure of 50 Atmospheres Does Not Prevent Evolution of Hydrogen by Nitrogenase,” Science. 224:1095-7 (1984)). However, a strategy to identify microbe strains, either naturally occurring or mutant forms, which have uncoupled hydrogen production from nitrogen fixation so that hydrogen production is metabolically advantageous to the growth and survival of the organism may represent a suitable means to develop a commercially efficient biocatalyst for hydrogen production.
The present invention is directed to achieving this objective.